Developing apparatus for electrophotography

ABSTRACT

THERE IS DISCLOSED HEREIN A DEVELOPING APPARATUS, WHEREIN MAGNETIC BRUSHES ARE FORMED ON THE OUTER SURFACE OF A ROTATING CYLINDER CORRESPONDING TO THE POLES OF A MAGNET INSTALLED WITHIN THE ROTATING CYLINDER, THE PHOTOSENSITIVE SURFACE OF A SHEET OF PHOTOSENSITIVE PAPER BEARING AN ELECTROSTATIC LATENT IMAGE IS BRUSHED TWICE BY THE MAGNETIC BRUSHES, AND THE PHOTOSENSITIVE PAPER IS FED WITHOUT USING ANY SUPPORT SO THAT ANY SIZE OF PHOTOSENSITIVE PAPER MAY BE USED AND MAY BE FED CONTINUOUSLY, TONER CAN BE SUPPLIED AND DISCHARGED EASILY, AND A GOOD QUALITY IMAGE CAN BE OBTAINED QUICKLY.

P 1971 YUTAKA KOlZUMI 3,606,865

mzvmorme APPARATUS FOR ELECTROPHOTOGRAPHY Filed May 28, 1969 Fig. 2

Unit ed States Patent 3,606,865 DEVELOPING APPARATUS FOR ELECTROPHOTOGRAPHY Yutaka Koizumi, Yokohama-shi, Japan, assignor to Kabushiki Kaisha Ricoh, Tokyo, Japan Filed May 28, 1969, Ser. No. 828,582

Claims priority, application Japan, June 8, 1968, 43/48,135, 43/48,136 Int. Cl. Bb 5/00 US. Cl. 118-637 6 Claims ABSTRACT OF THE DISCLOSURE There is disclosed herein a developing apparatus, wherein magnetic brushes are formed on the outer surface of a rotating cylinder corresponding to the poles of a magnet installed within the rotating cylinder, the photosensitive surface of a sheet of photosensitive paper hearing an electrostatic latent image is brushed twice by the magnetic brushes, and the photosensitive paper is fed without using any support so that any size of photosensitive paper may be used and may be fed continuously, toner can be supplied and discharged easily, and a good quality image can be obtained quickly.

The present invention relates to a developing apparatus for electrophotography, and in particular, to a developing apparatus for dry-type electrophotography developing a latent image on photosensitive paper with magnetic brushes.

The dry-type electrophotography is well known, in which photosensitive paper is coated with a photoconductive material dissolved in a binder, and a latent image is formed on a sheet of photosensitive paper by the process of electrically charging and exposing the paper. Toner, composed of carbon black and the like and mixed with iron powder is attracted to a magnet so as to form magnetic brushes, and the photosensitive surface of the photosensitive paper containing the electrostatic latent image is brushed with said magnetic brushes to make the electrostatic latent image visible. In a developing apparatus for the above-mentioned dry-type electrophotography using magnetic brushes, a magnet is installed within a rotatable cylinder, the magnetic brushes are formed upon the outer surface of the rotatable cylinder in line with or adjacent to the magnetic poles, and photosensitive paper is fed linearly by a movable support whereby the photosensitive surface of the photosensitive paper is brushed by the magnetic brushes. In such a developing apparatus, the method of supporting photosensitive paper by a photosensitive paper support is complex, and the size of photosensitive paper usable is generall limited by the size of the supporting surface of the support. Moreover, since the motion of the support is linear, it is necessary to move it back and forth. Therefore, the reproduction efiiciency is low and the supply of toner during the process of development becomes very difficult.

It is an object of the present invention to provide a developing apparatus of the type described in which magnetic brushes are formed on the outer surface of a rotating cylinder in line with or adjacent to the opposite poles of a magnet installed within the rotating cylinder, the photosensitive surface of a sheet of photosensitive paper containing an electrostatic latent image is brushed twice in sequence by the magnetic brushes, and the photosensitive paper is fed without using any support so that any size or continuous web of photosensitive paper used and may be fed, toner can be supplied and discharged easily, and a superior quality image can be rapidly obtained.

It is another object of the present invention to provide a developing apparatus for developing the latent images on ice a photosensitive paper in which magnetic brushes are formed on the outer surface of a rotating cylinder in line with or adjacent to the opposite poles of a magnet installed within a rotatable cylinder, the photosensitive surface of a sheet of photosensitive paper containing an electrostatic latent image is brushed twice by said magnetic brushes in sequence, the photosensitive surface is moved in the direction opposite to the rotational direction of the cylinder to be brushed by means of said magnetic brushes, and linear guide members for preventing the magnetic brushes on the cylinder from curling the tip of the photosensitive paper are provided adjacent the cylinder in the path of movement of the photosensitive paper.

With these and other objects in view, which will become more readily apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawing, in which:

FIG. 1 illustrates a sectional view showing an embodiment of the developing apparatus in accordance with the present invention; and

FIG. 2 illustrates a sectional view of the main portion of the apparatus showing another embodiment.

In FIG. 1, a hollow rotatable cylinder 1 made of a non-magnetic material is supported on a shaft 2 rotatably journalled on a stationary frame (not shown) and having end plates fitted for rotation on the shaft 2. Within the cylinder 1, a magnet 3 is mounted about the axis 2 and fastened thereto by means of a key 4. Positioned above the cylinder 1, a container 6 filled with a developing powder 5 consisting of a mixture of toner and iron powder has a bottom aperture, whereby said developing powder is dropped through the aperture of the container 6 onto the outer surface of said rotatable cylinder 1 and attracted to the surface thereof through the magnetic force exerted by magnet 3. An ejector plate 7 is provided in the container 6 to discharge the developing powder 5 in predetermined measured quantities. The cylinder 1 is rotated clockwise by a suitable driving system (not shown in the drawing), and the developing powder attracted to its outer surface forms magnetic brushes 3a and 3b on the outer surface in line with or adjacent to both poles of said magnet 3. Above and below each pole of the magnet 3, rollers 9 and 10 interconnected by an endless belt 8 and rollers 12 and 13 interconnected by an endless belt 11 are rotatably journalled on the stationary frame. Cooperating rollers 14 and 15, rotatably journalled on the stationary frame are pressed against rollers 9 and 10 through contact belt 8, and similarly, rollers 16 and 17 rotatably journalled on the stationary frame are pressed against rollers 12 and 13. Between the rollers 14 and 15 and between the rollers 16 and 17, a plurality of adjacent, spaced linear guide members 18 and 19 are suspended whereby the endless belts 8 and 11 and the linear guide members 18 and 19 form paths for movement of photosensitive paper through the magnetic brushes 3a and 3b. At the upper ends of these paths of movement of the photosensitive paper, there are an inlet and an outlet for the infeed and egress of the photosensitive paper. The feeding inlet includes guide plates 20 and the outlet includes plates 21 attached to the stationary frame. The lower parts of the two paths of movement of photosensitive paper are interconnected by a guide plate 22 made of an accurately shaped porous plate or a net. The rollers 9 and 12 are rotated by a driving means (not shown in the drawing) in the direction of arrows a and b, respectively, and the belts 8 and '11 move in the direction shown by arrows c and a. respectively. The rotatable cylinder 1 is driven by this driving means and is rotated in the direction shown by an arrow e. A sheet or continuous web of photosensitive paper 23 containing a latent image is fed by the belt 8 into the infeed between the rollers 9 and 14 in the direction shown by the arrow c, its photosensitive surface being brushed by said magnetic brush 3a, and as a result, toner mixed with iron powder is attracted to the electrostatic latent image thereon whereby photosensitive paper 23 is developed. The photosensitive paper 23 thus developed is further fed by the belt 8 between the rollers 10 and 15, is reversed in direction of motion by the guide plate 22, is upwardly fed by the belt 11 between the rollers 13 and 17, is brushed by the magnetic brush 3b so as to be subjected to a second developing procedure. This second developing enhances the density of the developed image and eliminates any undesirable toner attracted to the background surface of the photosensitive paper 23. After the second developing, the photosensitive paper 23 is fed further by the belt 11 between the rollers 12 and 16 and conveyed along plates 21 out of the apparatus to undergo further processes as required, not forming a part of the present invention. The linear guide members 18 and 19 prevent the photosensitive paper 23 from deviating from its path after passing between the rollers 9 and 14 or between the rollers 13 and 17, due to an inherent paper curl or by the paper being curled by the magnetic brushes 3a and 3b. Underneath guide plate 22, a container 24 is provided which collects the discharged developing powder. Cleaners 25 and 26 may be provided are pressed gently against the belts 8 and 11, respectively, to brush off any toner attracted to those belts 8 and 11. The same type of cleaner may also be provided for every roller that is directly in contact with the developed photosensitive paper.

FIG. 2 illustrates a developing apparatus wherein instead of the linear guide members 18 and 19 made of iron wires shown in FIG. 1, a number of nylon threads 27 or other types of strings extend about the rotating shafts of the four rollers 14, 15, 16 and 17. All of the elements of FIG. 2 designated by the same reference numbers of FIG. 1 are indentical with those of the embodiment of FIG. 1. Thus, the material of the linear guide members and the method for mounting them are not limited to the disclosure of the present invention.

In the developing apparatus in accordance with the present invention in which the path of photosensitive paper is formed passing through the magnetic brushes 3a and 3b and the photosensitive paper 23 is developed twice, no special support for the photosensitive paper 23 is required, so that there is no limitation on the size of usable paper and the continuous feed of a continuous web of photosensitive paper is possible. Moreover, since the path for supplying developing powder to the rotating cylinder is not obstructed by photosensitive paper, it is possible to supply the developing powder readily during the process of developing, which results in a great improvement of the reproduction efiiciency, and a superior quality image having a high density and clean background is obtained, since a second developing sequence is provided for by the present apparatus.

Furthermore, according to the apparatus the cylinder 1 is rotated in the direction of the arrow e, the photosensitive paper 23 is moved past the points of the magnetic brushes 3a and 3b in the direction of the arrows c and d, that is, opposite to the direction of rotation of the cylinder 1, and since a number of linear guide members are mounted adjacent the cylinder 1 along the path of photosensitive paper, it is possible to increase the relative speed between the photosensitive paper and the 4 moving developer forming the brushes. Therefore it is possible to brush the photosensitive paper by the brushes of the developer at high speeds sufiiciently to obtain images of high density, and further, when the photosensitive paper is fed into the developing part along the cylinder, it is possible to prevent the leading edge of the photosensitive paper from deviating from its path of movement because of the restraint of the magnetic brushes of the cylinder. Furthermore, the direction of the rotation of the rotating cylinder and the direction of the movement of the photosensitive paper may be opposite, and are not limited to the directions of the arrows shown in the drawing.

What is claimed is: 1. An electrophotographic developing apparatus comprising:

an electrically insulative cylinder rotatably mounted relative to a fixed magnet therein having substantially horizontally aligned fields of magnetic poles;

means for feeding a magnetic carrier toner mix onto said cylinder thereby forming a magnetic brush on the outer surface of said cylinder at each of said poles; means defining a path about said cylinder and through each magnetic brush for the passage of a substrate bearing a latent image to be developed; and

said means defining a path also comprising means to feed said substrate sequentially through each of said magnetic brushes.

2. A developing apparatus as claimed in claim 1, wherein said means to feed includes linear guide members postioned along the travel path of said substrate in at least the region of contact of said paper with said magnetic brushes.

3. A developing apparatus as claimed in claim 1, wherein said means to feed includes guide means for conveying said substrate from its point of contact with the magnetic brushes adjacent one pole of the magnet to the second point of contact with the magnetic brushes adjacent the opposite pole of the magnet.

4. A developing apparatus as claimed in claim 3 wherein said guide means comprises an arcuate guide surface adapted to change the direction of passage of said substrate after contact of the latter by a first set of said magnetic brushes so as to contact a second set of said magnetic brushes whereby the latent image on said paper is further developed.

5. A developing apparatus as claimed in claim 2 wherein said linear guide members are adapted to move along the path of passage of said substrate in unison with said paper.

6. A developing apparatus as claimed in claim 1 wherein said substrate moves past the magnetic brushes on said rotatable cylindrical means in a direction of movement opposite to the direction of rotation of said cylindrical means.

References Cited UNITED STATES PATENTS 3,058,405 10/1962 Limberger 1l8-637X 3,176,652 4/1965 Mott et al 118-637 MORRIS KAPLAN, Primary Examiner 

